For example, in a power conversion device such as a voltage type PWM inverter which controls an operation with a motor being defined as a load, a carrier frequency of the voltage type PWM inverter has recently been increased with expansion of applications and improvement in characteristics of a power semiconductor element.
With increase in frequency of such a voltage type PWM inverter, electromagnetic interference (EMI) caused by the voltage type PWM inverter has posed a serious problem.
The cause of electromagnetic interference by the voltage type PWM inverter mainly resides in a current which flows through a ground line.
In this connection, Japanese Patent Laying-Open No. 10-94244 has proposed a scheme for lowering a leakage current by suppressing a common mode voltage output from the inverter by using an active element.